I’ve shared this tip before, but I still get a lot of questions about how to view the Facebook chat windows in full screen.
Start by opening Facebook in your browser. Click the message icon at the top-right of the page.
Then choose See All in Messenger at the bottom of the menu that appears.
While the chat window doesn’t take up the full screen, it’s a good half of the screen and quite larger than that little chat box.
To find a friend, you can type their name at the left.
Just type your conversation in the center box and hit Send to send the message.
To go back to your Facebook feed, just click Home at the left